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Feasibility of a tetracycline-binding method for detecting synovial fluid basic calcium phosphate crystals. Arthritis Rheum 2008 Oct;58(10):3270-4 PMID: 18821676 PMCID: PMC2574625

Pubmed ID





OBJECTIVE: Basic calcium phosphate (BCP) crystals are common components of osteoarthritis (OA) synovial fluid. Progress in understanding the role of these bioactive particles in clinical OA has been hampered by difficulties in their identification. Tetracyclines stain calcium phosphate mineral in bone. The aim of this study was to investigate whether tetracycline staining might be an additional or alternative method for identifying BCP crystals in synovial fluid.

METHODS: A drop of oxytetracycline was mixed with a drop of fluid containing synthetic or native BCP, calcium pyrophosphate dihydrate (CPPD), or monosodium urate (MSU) crystals and placed on a microscope slide. Stained and unstained crystals were examined by light microscopy, with and without a portable broad-spectrum ultraviolet (UV) pen light. A small set of characterized synovial fluid samples were compared by staining with alizarin red S and oxytetracycline. Synthetic BCP crystals in synovial fluid were quantified fluorimetrically using oxytetracycline.

RESULTS: After oxytetracycline staining, synthetic and native BCP crystals appeared as fluorescent amorphous aggregates under UV light. Oxytetracycline did not stain CPPD or MSU crystals or other particulates. Oxytetracycline staining had fewer false-positive test results than did alizarin red S staining and could provide estimates of the quantities of synthetic BCP crystals in synovial fluid.

CONCLUSION: With further validation, oxytetracycline staining may prove to be a useful adjunct or alternative to currently available methods for identifying BCP crystals in synovial fluid.

Author List

Rosenthal AK, Fahey M, Gohr C, Burner T, Konon I, Daft L, Mattson E, Hirschmugl C, Ryan LM, Simkin P


Todd W. Burner MD Assistant Professor in the Medicine department at Medical College of Wisconsin
Irina Konon MD Assistant Professor in the Medicine department at Medical College of Wisconsin
Ann K. Rosenthal MD Vice Chair, Chief, Professor in the Medicine department at Medical College of Wisconsin


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MESH terms used to index this publication - Major topics in bold

Calcium Pyrophosphate
Feasibility Studies
Microscopy, Ultraviolet
Sus scrofa
Synovial Fluid
jenkins-FCD Prod-332 f92a19b0ec5e8e1eff783fac390ec127e367c2b5